a) FIELD OF THE INVENTION
This invention relates to a novel method for measuring eccentricity which does not depend on the accuracy of a reference cylindrical surface.
b) DESCRIPTION OF THE PRIOR ART
The measurement of eccentricity of a rotary axis has been made by detecting whether a fiducial point provided on the rotary axis produces a perfect circle, with the rotation of the rotary axis, in a plane perpendicular to it. In this case, the detection of roundness is performed on the basis of a coincidence with a reference cylindrical surface produced with sufficient accuracy or of the locus of a rotary axis making use of a cylindrical surface produced with sufficient accuracy. However, the accuracy of the cylindrical surface for reference depends on the machining tolerance of machine tools and operator skill. Consequently, as the accuracy of the eccentricity measurement is to be improved, it becomes difficult to make the reference cylindrical surface with a higher degree of accuracy. For instance, if the tolerance of the order of 1 nm is imperative, such difficulty will greatly increase.